Another new form of Neurostimulation for the treatment of depression came to my attention: transcranial direct current stimulation (tDCS).
What is transcranial direct current stimulation?
With tDCS a weak electrical current of 1 or 2 m Ampere is applied to the head with an electrode. The electrode is a non-metalic conductive rubber electrode, covered completely by saline soaked sponges.It is a noninvasive brain stimulation technique that utilizes low amplitude direct currents applied via scalp electrodes to inject currents in the brain and thus modulates the level of excitability. It doesn’t elicit seizures and it doesn’t require anesthesia. For comparison in ECT current of 9 m Ampere is used to elicit seizures during narcosis.
A recent article about this “treatment” was published: A randomized, double-blind clinical trial on the efficacy of cortical direct current stimulation for the treatment of major depression.
The abstract describes a double blind parallel placebo controlled trial. In other words, depressed patients were divided in three groups, one that received the actual treatment, one group that received an active control treatment and a group that received a placebo treatment. Active control was stimulation of the occipital cortex which is assumed to be without antidepressant potential. The placebo group received the treatment without the actual stimulation, active treatment was anodal tDCS of the left dorsolateral prefrontal cortex.
Mood was evaluated by a blinded rater using the Hamilton Depression Rating Scale (HDRS) and by a self evaluation scale the Beck Depression Inventory (BDI).
The reduction in severity score on the HDRS was significantly larger for the active treatment compared to occipital and sham tDCS. Again although significant the question remains how clinical relevant. More clinical outcome such as response ( 50% or more reduction on HDRS compared to baseline) and remission (absolute HDRS score below 7) are not provided. This makes the clinical relevance of the data hard to compare. The beneficial effects of tDCS in the DLPFC group persisted at least for 1 month after the end of treatment.
On ClinicalTrials.gov 17 studies with tDCS are recorded. Two of them are recruiting depressed patients for efficacy and safety of tDCS. One study in New York State Psychiatric Institute USA the other in The University of New South Wales, Australia.
A PubMed search for tDCS and depression results in 19 publications.
A website of The Center for Noninvasive Brain Stimulation has more information about tDCS and also rTMS.
This picture is from tmslab.org:
Dr Shock’s opinion
This treatment has something magical about it. This increases the placebo effect. Moreover side-effects were minimal. It is hard to understand how local excitation of the cortex could influence serious alterations of the hypothalamic-pituitary-adrenal axis (HPA axis) present in some depressed patients or other neurobiological alterations for that matter.